(1) The physical characterization and identification of a representative RNA-virus, turnip crinkle virus, was achieved at the nanogram load level, as required by many clinical and biological applications. The method is based on silver stained electropherograms on thin-layer agarose gel strips. (2) Meningitis immunogen preparations of varying immunogenicity exhibit populations with an identical surface charge density in 2- dimensional agarose gel electrophoresis. Sizes vary from 10 to several hundred nm in radius. The evaluation of gel electrophoretic patterns by computer methods appears promising as a tool for quality control in the production of a meningitis vaccine. (3) The proteolytic digestion products of human and bovine fibrinogen are quantitatively and qualitatively distinct by the criterion of their SDS-PAGE patterns. (4) Three components of a subcellular particle from X. laevis with 5' pre-tRNAase activity were separated by agarose gel electrophoresis and silver staining. (5) The size and net charge relations between a DNA fragment of 155 bp carrying a central protein binding site and the same fragment with a peripheral binding site were investigated.